1. Technical Field
Methods of processing an article formed of a static dissipative ethylene tetrafluoroethylene (ETFE) resin, such an such as to reduce an electrical resistivity and/or to increase a tensile strength of the article, and ETFE-based articles produced in accordance with methods disclosed herein.
2. Related Art
Poly(ethylene-co-tetrafluoroethylene), commonly referred to as ethylene tetrafluoroethylene, or ETFE, is a polymer having a relatively high melting temperature, relatively high corrosion resistance and strength over a relatively wide temperature range, and relatively high electrical and high-energy radiation resistance properties. ETFE also tends to have better mechanical toughness and chemical resistance compared to polytetrafluoroethylene (PTFE), a synthetic fluoropolymer of tetrafluoroethylene, such as DuPont Teflon®.
ETFE is used in space, nuclear, and aviation industries for cable ties and wire coatings. ETFE based cable ties tend to have a relatively high strength to weight ratio and relatively low outgassing characteristics.
ETFE also tends to have relatively high volumetric and surface electrical resistivity, which may lead to electrical charging or static build-up. For example, in an extraterrestrial environment, elements of a spacecraft or satellite may become electrically charged due to photoelectric effects (sunlight) and/or electron flux. Satellites in geosynchronous orbits are particularly susceptible to electron flux found in outer regions of the outer radiation belt.
Another concern is deep dielectric discharge (DDD). In a flux of relatively high-energy electrons, electrons may penetrate an outer surface of a spacecraft and enter dielectric materials such as circuit boards and coaxial cable insulation.
When the charge build-up exceeds a threshold, such as a dielectric strength of a material, the charge may suddenly discharge to and/or through other elements, such as electrical circuits and/or sensors. This may cause severe and potentially catastrophic damage.
An ETFE resin may include carbon black or other additive to provide a measure of static dissipation. For example, a Tefzel® HT-2170 fluoropolymer is marketed by E.I. du Pont de Nemours and Company, of Wilmington, Del., U.S.A., as a static-dissipating semi-conductive resin. According to marketing materials, DuPont™ Tefzel® fluoropolymers are melt-processible thermoplastics, and are part of a family of fluorine-based products that include Teflon® PTFE, Teflon® FEP, and Teflon® PFA fluoropolymers resins.
It has been observed that, while a sheet formed of such a static dissipative resin may have an electrical resistivity as low as 1.4 Mega Ohms as measured between points located over approximately 4 inches apart, cable ties formed from the resin have been observed to have an electrical resistivity several orders of magnitude greater.